This invention relates to sonar simulators for training purposes or the like, and more particularly to improved simulation of reverberation background noise resulting from an actively pinging sonar detecting-ranging set. This background noise consists of reflections of transmitted acoustic energy from the ocean bottom, ocean surface, and the ocean itself in the immediate vicinity of the hydrophones. The characteristics of each reflective component resulting from a single transmission, as well as the time relationship between the components, vary with the physical conditions of the situation. Each reverberation signal component consists of an envelope of audio frequency pulses, the shape and amplitude of which is a function of those physical conditions. In general, simulation of reflected sonar signals, either target or background, has been accomplished through systems including RC pulse shaping networks, timing means such as counters, attenuators, and oscillator means such as basic voltage controlled oscillators, in combination to produce the simulated sonar signals. Such systems have been notably complex and have usually required instructor controlled inputs.